Engine Tick and Temp Range Shift

specops1526

Well-known member
Jan 17, 2007
845
11
Los Angeles, CA
Having a new issue and hoping someone here has some thoughts on cause.

Background on truck: '04 DII, 76K miles, Short block replaced at 50k by LRNA due to slipped liner, 180* soft spring thermostat, new expansion tank, newer radiator and hoses, fresh oil change from Mobil 1 0w-40 to Mobil 1 10w-40 High Mileage (badly needed as oil was dirty and old as shit).

Truck has been running great for a long time without any issues. Recently noticed a leak at the seam in the expansion tank so my mechanic replaced it. New one developed the same leak so that one was replaced. Ever since the first replacement, the truck has been running a bit hotter according to my ScanGuage. Normal temp range was 184-200* (exact same as my other '04 running the 180 T-stat). Now the temp range has shifted to 197-209*. So the range is about the same but it has shifted to higher temps. Seems to get hotter on hard acceleration too, maxing out at 209-211.

Also, I've got a ticking while in gear upon medium acceleration from 0-40/45ish mph. It sounds like that throaty diesel engine noise and sounds like it's coming from the passenger side. Doesn't happen while idling in neutral and with revving in neutral. Seems to go away with harder acceleration and faster speeds, but it could just be getting faster as well as being drowned out by normal engine noise.

Any thoughts on causes? Could my Thermostat be failing already? It's probably only a year old. Could the tick be an exhaust leak? My mechanic claims he couldn't find one and that he did a pressure test with no bad results. (clearly he will need to look deeper since nothing has changed since he worked on it)

Thanks
 

Hubacek

Well-known member
Apr 28, 2015
88
0
Dallas, TX
air pocket in cooling system. try bleeding it off. do you have hot air if you turn up the temp on your cabin controls? I would start there. cold air means definitely an air pocket, but I would still suspect an air pocket either way.
 

specops1526

Well-known member
Jan 17, 2007
845
11
Los Angeles, CA
air pocket in cooling system. try bleeding it off. do you have hot air if you turn up the temp on your cabin controls? I would start there. cold air means definitely an air pocket, but I would still suspect an air pocket either way.

I thought about that too. I've run the heat on high while driving on the highway and still the same. Definitely getting hot air in the cabin. I'll try some of the other bleeding techniques to see if those work.
 

specops1526

Well-known member
Jan 17, 2007
845
11
Los Angeles, CA
Bringing this back up. Ticking/fluttering turned out to be an exhaust leak from a bad manifold gasket. It's mostly fixed but I feel like I hear it a little bit if I listen for it...

The temp issue is still there. Mechanic says he replaced the T-stat and vacuum filled the coolant. Heat is fine, even on acceleration. Took reservoir cap off and I see a constant stream of coolant so I'm guessing there is no air. I may try the upper hose bleed screw this weekend to make sure.

Any other thoughts on this odd temp shift? Previous temps were 188-195. Now I'm always at 200-209.

I know this isn't in the overheating range but to me, this indicates and issue somewhere. I'm interested in fixing it before it becomes a bigger issue.
 

rovercanus

Well-known member
Apr 24, 2004
9,643
244
Be aware that exhaust leaks that sound like it's coming from the manifold can also be leaking through the head gasket.
 

mbrummal

Well-known member
Jan 23, 2009
2,893
22
Willow Spring, NC
How much has the ambient temp changed? The stock (and 180*) thermostat makes the engine run warmer in colder weather because a portion of the sensing element is exposed to the cooler coolant returning from the radiator. Cooler weather means cooler coolant returning from the radiator. The RAVE manual explains it in more detail.
 

specops1526

Well-known member
Jan 17, 2007
845
11
Los Angeles, CA
Yeah, thought about testing the coolant for gas. Will have to do that when I have some time.

Ambient temp is much cooler but my other '04 with the same Tstat is operating at the normal range of 186-195*. The one with the temp shift has to have something wrong with it in my mind...
 

specops1526

Well-known member
Jan 17, 2007
845
11
Los Angeles, CA
Yep. Dark Grey. Purchased this part# PEL500110G.

As I mentioned, it was driving in the 186-195* range for a year or more. Now after some work on the truck, it's up to 197-209*.

Would a slight leak in the head gaskets cause this behavior?
 

specops1526

Well-known member
Jan 17, 2007
845
11
Los Angeles, CA
Hmmm, I think the culprit ended up being a bad temp sensor but I can't fully remember. Changed out the Tstat a couple of times and then put the 180 back in. Changed the coolant overflow a couple of times too. Temp went back to normal with no more rise. I sold the truck sadly at the end of 2017 but it was running really good when I did. Now I'm down to just 1 '04 Disco that still runs in the 186-195/197 temp range.